Matrix for electroforming foraminous sheets



Dec. 24, 1940.

E I., v 'l f3 E. o. NoRRls 2,226,382

MATRIX FOR ELECTROFORMING FORAM'INOUS SHEETS Filed April 22, 1958 2 Sheets-Sheet 1 INVENTOR far/ARD Na/ws E. O. NORRIS Dec. 24, .1940.-

MATRIX FoR ELECTROFORMING FoRAMINoUs SHEETS l Filed April 22, 1938 2 Sheets-Sheet 2 INVENTOR Y [0n/Ana Q Nam/5 BY l ,f ATTORNEY Pienred 1392.24, 1940 PATENT OFFICE MATRIX FOR ELECTROFORMING FORAM- INOUS SHEETS Edward 0. Norris, Westport, Conn., assig-nor to Edward 0. Norris, Inc., New York, N. Y., a corporation of New York Application April 22, 1938, Serial No. 203,504

Claims.

This invention relates to the electroformation of reticulated sheet material but more particularly relates toa matrix on which such electroforming may take place, and the process of pro- 5 ducing the matrix. The particular matrix described is adaptable for the production of foraminous sheet suitable for dials, stencils, or the like, or as screen for filtering liquids, segregatingk material, grading material to size, ex-

clusioxr .of insects from buildings, photo-en- Vgravers use, and in fact for any purpose that such a fabric is adapted to serve.

In the matrix which I am about to describe, one important object that is accomplished is l5 that of making possible the production of what foraminous sheet is electrolytically deposited on a matrix, the lands of which are flush with the 'electrically non-conductive areas, the deposit builds laterally at twice the rate at which it builds in thickness, and before the desired thickness is obtained the lateral encroachment of the deposit over the insulated areas has progressed so far that the process must be discontinued or else the holes Will either be closed up or nearly so. For many purposes screen made in such a manner is too thin compared with its hole size and land width. By my present process I am able to electrolytically deposit foraminous sheet which has a relatively high ratio of thickness to hole size.

I accomplish my object by employing a matrix the exposure surface of which con-sists of crossed channels or valleys the bottoms of which are of metal or other material capable of receiving an electrolytic deposit and the walls of which are defined by protuberances projecting above the metal surface of the base plate. These walls are composed wholly or partly of material, the surface of which is inactive to electrolytic deposition, which material I will refer to for purposes of this specification as passive material. Most passive material that is available for the purpose described is relatively fragile or disintegrable by the action of acids, alkalies, and other chemical and electrolytic reactions, or is only mildly adherent to a metallic surface, or it may have all of these and other defects which offer diiculties in using it as passaive material in matrices of this character. A matrix for the purpose I have described must, in order to be commercially useful, be strong, not readily attacked by chemical action in an electrolytic bath, and must be reasonably resistant to destructure effects which result from stripping an electroformed; deposit therefrom. All of the above difficulties are overcome to a very great extent, and all the advantages above referred to and others are accomplished by my invention.

This application `contains matter taken from my United States Patents Nos. 2,166,366 and 2,166,267, issued July 18, 1939.

Referring to the drawings,

Fig. l is a view in perspective of a metal plate in which a large number of pits have been formed for the reception of passive material;

Fig. 2 is a detailed sectional View in elevation along the line 2-2 of Fig. 1 but showing, in addition, further steps in the process;

Figs. 3, 4, and 5 are likewise detailed sectional views showing further steps in the preferred process, Fig. 5 illustrating the detail construction of the complete matrix;

Fig. 6 and Fig. '7 are views in sectional elevation showing a modified form of the process and a modified constructionA of matrix;

Figs. 8 and 9 show a still further modified process and modified construction of matrix;

Figs. 10, 11, 12, and 13 show a still further modified process of a further modified type of matrix.

Referring first to the preferred process and matrix illustrated by Figs; 15,both inclusive, a base plate I0 of copper, nickel or other electrically conductive material is provided on at least one face with pits or depressions II, the plate thus presenting a surface with the lands I2 crossing each other at the junction areas I3. These pits may be created by any suitable process, but a convenient way is'that described in my application Ser. No. 52,334 above referred to and, briefly stated, consists in first coating the surface to be pitted with light-sensitized photo-engravers glue, photoprinting on the lm'of glue areas defined by the lands I2 (which may be accomplished by exposing the glue film to light through a negative of a half-tone screen) then developing and Washing out, and thereafter etching to produce the pits.

The plate of Fig. 1 having been produced, the pits II are then filled with shellac or other passive substance `I4 (see Fig. 2) and the entire surface including the lands I2 and junction areas I3 together with the exposed areas of shellac is smoothed down by any suitable method such as rubbing and polishing with abrasivc:T and polishing powders.

The lands and junction areas are then covered with a stripping film I5-i. e., a film of material which, while still permitting of the reception of an electrolytic deposit, nevertheless permits the deposit to be stripped therefrom. In practice, of course, the shellac areas would likewise be covered 'with the material of the film, but since the material of the lm is passive, it makes no dierence in the subsequent operations, which will now be described.

After the stripping iilm has been applied, the base plate it, with its shellac fillings Ml, is employed as a cathode for the'electrolytic deposition of some other metal than the metal of which the base plate is composed. 1f the base plate is of copper (which I prefer that it should be), the deposit I6 may be of nickel, for the reason that, as presently will appear, there are available methods for selectively dissolving copper to the exclusion of nickel.

The nickel I6 having been deposited, the shellac Iii is next thoroughly washed out of the pits I l by washing and scrubbing with alcohol, resulting in the structure shown in Fig. 3, the nickel i6 being slightly adherent to the base plate I6, although strippable therefrom by the exertion of comparatively little force.

The next step in the process is illustrated in Fig. li, whereinthe pits II are shown as filled in this particular case with vulcanizable rubber composition ll, the level of the filling however being carried not only to the edges of the pits but also to a level ush with the top surface of the nickel deposit.

'Ihe entire surface may then be dusted with ne powder of bronze, graphite or any other substance having the characteristic of electrical' conductivity and the whole may be employed as a cathode in an electrolytic bath and the deposit I3 laid thereon. The deposit I8 may be of nickel or copper or any other material which can be electrolytically united to the surface.

At this point the structure consists of the base plate Ill with the vulcanizable rubber composition llings il practically non-adherent thereto, the nickel deposit I6 likewise practically nonadherent to the base plate, and the deposit I8 which is rmly adherent to the rubber fillings and to the nickel deposit. 'I'he deposit I8 therefore may be then stripped from the base plate carrying with it the rubber composition llings and the nickel deposit I6, the whole constituting the unit illustrated in Fig. 5, and it will be noted ythat the rubber protuberances are firmly anchored by reason of the fact that they extend under what are, in effect, flanges I9 extending from the nickel deposit I6. In other words, they are not only strongly adherent to the deposit I8 but are also mechanically united therewith by an interlocking socket.

The unit shown in Fig. 5 may then be subjected to a vulcanizing process, the degree of vulcanization being however only such that the rubber protuberances il will yield readily to stripping of a deposit on the nickel bottoms 26 of the channels or valleys defined by the protuberances.

The unit illustrated by Fig. 5 may then after the bottoms. of the channels 26 have been coated with a thin of wax, chrome or other material that permits of a non-adherent electrolytic deposit, be employed as a cathode in an electrolytic bath, Fd the result will be a deposit of foraininous si et thereon. The walls of the protuberances confine the lateralA spread of the deposit, ....3 deposit may therefore be carried aaaaaaa to any thickness desired. When the deposit has been completed, it may be stripped from the matrix surface, the stripping film permitting its release from the metallic bottoms of the channels and the deformability of the vulcanized rubber protuberances permitting its release from them without injuring them or loosening or tearing them from their anchorages to the plate i8. The plate I0, aft-er being stripped from the matrix, may be used repeatedly for the production of additional matrices in the same manner as is above described with reference to the production of the matrix of Fig. 5.

in the modification of Figs. 6 and 7, the base plate 36 having been pitted as shown at Stand the pits iilled with passive material 32, is then subjected to cathodic electrolytic action until the backing 33 has been deposited to say the depth indicated by the broken line 34 of Fig. 6. Prior to applying this backing, the exposed surfaces of the passive material may be dusted with metallic or other electrically conductive powder in order that the fillings 32 shall adhere firmly thereto.

The plate with the fillings 32 may then be masked against corrosion by an etching reagent (which if the plate 30 be of copper may be ferric chloride) over all its parts except the surface 35, and etched from the plane indicated by the broken line 36 to* the plane indicated by the full line 3l. As will be seen, this results in a surface composed of channels or valleys the bottoms of which are of metal and the walls of which are of the passive material of the protuberances 38. The plate of Fig. 'l may be then used as a matrix for the electroforming of forarninous sheet in the same manner as in the case of the matrix of Fig. 5.

In the modification of Figs. 8 and 9, the plate 40 is shown as being provided with holes 4I extending from surface to surface. These holes may be produced in the same manner as pits Il of Fig. 1 except that the etching is carried entirely through the plate.l The holes may then be lled with passive material 42 and a metal deposit laid thereon in the same manner as is described with reference to the metal deposit 33 of Figs. 6 and 7, to the height say indicated by the broken line 43 of Fig. 8. The material deposited is indicated in Fig. 9 by the numeral 44. Then, after masking as in the case of Figs. 6 and 7, .the plate 40 with its backing 44 is etched until its surface 45 is brought to the plane indicated by the line i6 in Fig. 9, leaving projecting therefrom the protuberances 4l?. This plate may be used as a matrix for the electroforming of screen in the same manner as the plate of Fig. 7

In Figs. l0, 11, 12, and 13 a plate 50 is prepared in the same manner as is the plate of Fig. 1. Next, the stripping film is applied to the pitted surface of the plate, the stripping film covering not only the lands but the walls of the pits as well. 'I'he plate thus prepared is subjected cathodically to an electrolytic bath-say, of proper composition for copper deposition, and the plate 5I shown in section in Fig. 1l deposited thereon (see Fig. il). The plate 5l is, in fact, an electrotype of the pitted surface of the plate 56. The pits on one side of the plate 5l are then lled with passive material and the deposit 553 applied thereto, Without however employing a stripping lm. The deposit is therefore firmly adherent to the plate or electrotype Additional passive material is then inserted and becomes adherent to the passive material After smoothing off the surface, the plate 55 is then applied by electrodeposition or otherwise and Without interposition of a stripping film on the deposit 53.

The entire unit, comprising the plate 55, deposit 53, and masses of passive material 52 and 54, is stripped from the plate 5l and exhibits the construction shown in Fig. 12 with the protuberancs of passive material forming the Walls of channels or valleys, the bottoms of which are of metal. It will be observed that the protuberances are 'mechanically locked to the backing plate 55 by reason of the fact that the material runs under the flanges 56; also, it will be observed that the protuberances themselves slope slightly as shown at 51 to the bottoms of the channels. This unit constitutes a matrix suitable for the electroformation `of goraminous sheet as in the case of the previously described matrices.

To be more specific with respect to the nature of the passive material that I have referred to, there are a number of suitable materials for this purpose, among which I would mention Bakelite, asphaltum, shellac, varnish, various hard wax compositions, enamel including vitreous enamel, vulcanized natural rubber, and various synthetic rubbers. Other materials that' exhibit passivity to electrolytic deposition under certain conditions of operation are chrome and aluminum.

I have'described above certain embodiments 'of my invention and a preferred process with certain modifications thereof, but I wish it to be understood that these are illustrative and not limitative of my invention and that I reserve the right to make various changes in form, construction, and arrangement of parts and also to make various changes in process of manufacture falling within the spirit and scope of my inventions, as set forth in the claims.

I claim:

1. A matrix adapted to serve for the electroforming of foraminous sheet comprising a base plate presenting a surface adapted to receive an electrolytic deposit and a plurality of protuberances of readily deformable resilient electrolytically` passive material projecting from said base plate and mechanically interlocked therewith by means of a -ange embedded in said base plate.

2. A matrix adapted to serve for the electroforming of foraminous sheet comprising a base plate presenting a surface adapted to receive an leleotrolytic deposit and a plurality of protuberances of readily deformable resilient electrolytically passive material projecting from said base plate and socketed therein, the socketed connection comprising a flange embedded in the material of the base plate.

3. A matrix adapted rto serve for the electroforming of foraminous sheet comprising a base plate presenting a surface adapted to receive an electrolytic deposit and a plurality of lprotuberances of readily deformable resilient electrolytically passive material projecting from said base plate and extending into sockerts in the same, the said sockets being tapered in a convergent direction as they approach the said surface and those portions of the protuberances contained in such sockets being likewise tapered to conform to the taper of fthe sockets.

4. A matrix adapted to serve for the electrovforming of foramirnous sheet comprising a base plate presenting a surface adapted to receive an electrolytic deposit and a. plurality of protuberances of material having the resilience and deformable characteristics of pantially vulcanized rubber projecting from said base plate and mechanically-interlocked therewith by socketing in the same, the socketed connection comprising a ange about the rubber projection said flange being embedded in the material of the base plate.

5. A matrix adapted to serve for ,the e1ectro. forming of foraminous sheet comprising a base plate presenting a surface adapted to receive an electrolytic deposit and a plurality of protuberances of resilient and readily deformable rubber projecting from said base plate and mechanically interlocked therewith, the interlock being effected by means of flanges on rthe rubber projections embedded in the material of the base plate.

EDWARD O. NORRIS. 

